Method to achieve low and stable ferromagnetic coupling field

ABSTRACT

A method for making a spin valve includes providing a substrate; depositing a first ferromagnetic layer having a first surface on the substrate; depositing a spacer layer having a second surface; depositing a second ferromagnetic layer, wherein the spacer layer is disposed between the first and second ferromagnetic layers; and exposing one or more of the first and second surfaces to an oxygen partial pressure, then decreasing the oxygen partial pressure before depositing a subsequent layer. One or more of the first and second surfaces may be exposed to an oxygen partial pressure of between about 1×10 −7  Torr and about 5×10 −5  Torr.

This application is a divisional of application Ser. No. 09/618,167,filed on Jul. 17, 2000, now U.S. Pat. No. 6,661,622.

FIELD OF THE INVENTION

This invention relates generally to spin valves. More particularly, itrelates to the coupling field of spin valves.

BACKGROUND ART

A spin valve or a magnetoresistive (MR) sensor detects magnetic fieldsignals through the resistance changes of a read element, fabricated ofa magnetic material, as a function of the strength and direction ofmagnetic flux being sensed by the read element. The conventional MRsensor operates on the basis of the anisotropic magnetoresistive (AMR)effect in which a component of the read element resistance varies as thesquare of the cosine of the angle between the magnetization in the readelement and the direction of sense current flow through the readelement. Such a MR Sensor can be used to read data from a magneticmedium. An external magnetic field from the magnetic medium (the signalfield) causes a change in the direction of magnetization in the readelement, which in turn causes a change in resistance (ΔR/R) in the readelement and a corresponding change in the sensed current or voltage.

A spin valve has been identified in which the resistance between twouncoupled ferromagnetic layers varies as the cosine of the angle betweenthe magnetizations of the two layers and is independent of the directionof current flow.

An external magnetic field causes a variation in the relativeorientation of the magnetization of neighboring ferromagnetic layers ina spin valve. This in turn causes a change in the spin-dependentscattering of conduction electrons and thus the electrical resistance ofthe spin valve. The resistance of the spin valve thus changes as therelative alignment of the magnetizations of the ferromagnetic layerschanges.

Typically, a conventional simple spin valve comprises a ferromagneticfree layer, a spacer layer, and a single-layer pinned ferromagneticlayer, which is exchange-coupled with an anti-ferromagnetic (AF) layer.In an anti-parallel (AP) pinned spin valve, the single-layer pinnedferromagnetic layer is replaced by a laminated structure comprising atleast two ferromagnetic pinned sublayers separated by one or more thinnon-ferromagnetic anti-coupling sublayers.

In general, the larger the value of ΔR/R and the smaller the couplingfield H_(f), the better the performance of the spin value. The ΔR/Rvalue of a spin valve conventionally increases as the thickness of thespacer layer decreases due to the reduced shunting of the sense currentin the spacer layer of the spin valve. For example, a spin valve with acopper spacer layer having a thickness of 28 Å will achieve a ΔR/R ofabout 5%. If the thickness of copper spacer is reduced to 20 Å, a ΔR/Rof 8% will be obtained. However, the ferromagnetic coupling field H_(f)also increases as the thickness of the spacer layer decreases. Inaddition, the ferromagnetic coupling field of conventional spin valvesis unstable upon annealing cycles. For example, the ferromagneticcoupling field of spin valves changes from about +5 Oe at the beginningof the annealing process to +20 Oe after annealing cycles.

An article entitled “Oxygen as a Surfactant in the Growth of GiantMagnetoresistance Spin Valve” published Dec. 15, 1997 by Journal ofApplied Physic to Egelhoff et al. discloses a method for increasing thegiant magnetoresistance of ΔR/R of Co/Cu spin valves with use of oxygen.In this method, oxygen is introduced in an ultrahigh vacuum depositionchamber with an oxygen partial pressure of 5×10⁻⁹ Torr during depositionof the spin valve layers, or the top copper surface is exposed to theoxygen to achieve an oxygen coverage, after which growth of the sampleis completed. The oxygen acts as a surfactant during film growth tosuppress defects and to create a surface that scatters electrons morespecularly. Oxygen coverage decreases the ferromagnetic coupling betweenmagnetic layers, and decreases the sheet resistance of spin valves.

Unfortunately, this technique requires a very small oxygen partialpressure window around 5×10⁻⁹ Torr, since when the oxygen partialpressure is increased to only 10⁻⁸ Torr, all GMR (ΔR/R) gain due tooxygen is lost, and at oxygen pressures higher than this, the fall-offin GMR is rapid. This very small oxygen partial pressure is verydifficult to achieve or to maintain in a large manufacturing typesystem. Also, oxygen exposure of only one surface of the copper spacerlayer does not optimize the ferromagnetic coupling field. Furthermore,the use of oxygen for all spin valve layer depositions may result inoxidation of Mn in anti-ferromagnetic materials, such as FeMn, PtMn,IrMn, PdPtMn and NiMn, and thus kills the spin valve effect. Thereforethis technique can not be applied for spin valve deposition.

In addition, adsorbing oxygen only on the copper surface does notimprove the GMR, and produces only a positive coupling field.Furthermore, this technique results in a decrease in sheet resistance,which reduces the overall signal. Finally, prior art oxygen treatmentdoes not show stabilization of the ferromagnetic coupling field uponhard bake annealing cycles.

There is a need, therefore, for an improved method of making spin valvesthat overcomes the above difficulties.

OBJECTS AND ADVANTAGES

Accordingly, it is a primary object of the present invention to providespin valves with low and stable coupling field H_(f).

It is a further object of the invention to provide spin valves with highmagnetoresistive ratio ΔR/R.

It is another object of the invention to develop a process of makingspin valves with oxygen partial pressure levels can be used inmanufacturing systems.

It is another object of the invention to develop a process of makingspin valves achieving negative coupling fields in production processes.

It is a further object of the invention to develop a process of makingspin valves, which does not result in reduction in sheet resistance.

It is another object of the invention to develop a process of makingspin valves, which can be used with metallic anti-ferromagneticmaterials or oxide in addition to oxide antiferromagnetic materials.

It is an additional object of the invention to provide a method ofmaking spin valves having the above properties, which can be applied forbottom and top spin valves.

SUMMARY

These objects and advantages are attained by spin valves having a firstsurface of one ferromagnetic layer and a second surface of a spacerlayer, treated with oxygen.

According to a first embodiment of the present invention, a simple spinvalve includes a ferromagnetic layer having a first surface, such as aferromagnetic free layer, and a spacer layer having a second surface.One or more of the first and second surfaces has been treated withoxygen after deposition of the corresponding layers and oxygen treatmenthas been shut off before depositing a subsequent layer. Treatment withoxygen herein refers to exposing a surface of a layer of material tooxygen after the layer has been deposited. Physisorbed oxygen on thesesurfaces limits the intermixing between the layers and reduces thesurface roughness of the surfaces. As a result, the coupling field isreduced. The obtained coupling field is around −10 Oe for about 20 Åcopper, and the coupling field is stable upon hard bake annealing cyclesat 232° C. for 11 hours or at 270° C. for 6 hours. Furthermore, themagnetoresistive ratio ΔR/R is enhanced from about 6% to about 9%.

According to a second embodiment of the present invention, a bottomAP-pinned spin valve includes a first surface of a ferromagnetic layer,which is an AP-pinned sublayer, and a second surface of a spacer layer,treated with oxygen. The effect of oxygen surface treatment in AP-pinnedspin valves is similar to the effect of oxygen surface treatment insimple spin valve as described in the first embodiment.

A method of making spin valves having surfaces treated with oxygen isdescribed in a third embodiment of the present invention. An ion beamsputtering technique may be used to make the spin valves. A substrate isprovided in a vacuum chamber. A first ferromagnetic layer, Which may bea free layer for a top spin valve or a pinned layer for a bottom spinvalve, is deposited onto the substrate. A first surface of the firstferromagnetic layer is exposed to an oxygen-rich atmosphere with oxygenpartial pressure of between about 1×10⁻⁷ Torr and about 5×10⁻⁵ Torr, byintroducing an oxygen burst into the vacuum chamber for about 30seconds. The oxygen molecules are directed toward the substrate, and asubstrate shutter is fully open to directly expose the oxygen beam.Oxygen is physisorbed on the first surface. After about 30 seconds, theoxygen is shut off, and the normal process of fabrication of the spinvalve is resumed. A spacer layer of about 20 Å thick is deposited on theoxygen treated surface. A second oxygen burst is introduced into thevacuum chamber with an oxygen partial pressure of about 5×10⁻⁶ Torr fortreating a second surface of the spacer layer. The process of treatingthis second surface is similar to the process of treating the firstsurface as described above. The oxygen is again shut off before a secondferromagnetic layer, which may be a pinned layer for a top spin valve ora free layer bottom spin valve, is subsequently deposited.

The method described in the third embodiment may be used for top andbottom simple spin valves, top and bottom AP-pinned spin valves, anddual spin valves.

According to a third embodiment of the present invention, spin valves ofthe types depicted in the first and second embodiments, which are madeby the method described in the third embodiment, are incorporated in aGMR read/write head. The GMR read/write head includes a lower shieldlayer and an upper shield layer, which sandwich a spin valve, a lowergap disposed between the lower shield and the spin valve, and an uppergap disposed between the upper shield and the spin valve. The spin valveconverts a magnetic signal to an electrical signal by using themagnetoresistive effect generated by a relative angle betweenmagnetizing directions of a ferromagnetic free layer and a ferromagneticpinned layer.

A GMR read/write head of the type depicted in the fourth embodiment isincorporated in a disk drive system including a magnetic recording disk,a motor for spinning the magnetic recording disk, the read/write headand an actuator for moving the read/write head across the magneticrecording disk, according to a fifth embodiment of the presentinvention.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a cross-sectional schematic diagram of a top simple spin valveaccording to a first embodiment of the present invention;

FIG. 2 is a cross-sectional schematic diagram of a bottom AP-pinned spinvalve according to a second embodiment of the present invention;

FIGS. 3A–D are cross-sectional schematic diagrams illustrating the stepsof a process making spin valves with low and stable coupling fieldaccording to a third embodiment of the present invention;

FIG. 4 is a graph illustrating a plot of roughness as a function ofoxygen flow with copper spacer thickness of 20 Å for an AP-pinned spinvalve;

FIG. 5 is a graph illustrating a plot of sheet resistance as a functionof oxygen flow with the copper spacer layer thickness of 20 Å for anAP-pinned spin valve;

FIG. 6 is a graph illustrating a plot of magnetoresistive ratio ΔR/R asa function of oxygen flow with the copper spacer layer thickness of 20 Åfor an AP-pinned spin valve;

FIG. 7 is a graph illustrating a plot of coupling field as a function ofoxygen flow with the copper spacer layer thickness of 20 Å for anAP-pinned spin valve;

FIG. 8 is a graph illustrating a plot of coercive field as a function ofoxygen flow with the copper spacer layer thickness of 20 Å for anAP-pinned spin valve;

FIG. 9 is a graph depicting plots illustrating the properties ofAP-pinned spin valves as functions of copper spacer layer depositiontime with a constant oxygen flow of 2 sccm;

FIG. 10 is a graph depicting only two plots of magnetoresistive ratio(ΔR/R) and coupling field H_(f) as functions of copper spacer layerdeposition time illustrated in FIG. 9;

FIG. 11 is a schematic diagram of a GMR read/write head according to afourth embodiment of the present invention; and

FIG. 12 is a schematic diagram of a disk drive system according to afifth embodiment of the present invention.

DETAILED DESCRIPTION

Although the following detailed description contains many specifics forthe purposes of illustration, anyone of ordinary skill in the art willappreciate that many variations and alterations to the following detailsare within the scope of the invention. Accordingly, the followingpreferred embodiment of the invention is set forth without any loss ofgenerality to, and without imposing limitations upon, the claimedinvention.

FIG. 1 is a cross-sectional schematic diagram illustrating a layerstructure of a top simple spin valve 100 according to a first embodimentof the present invention. The spin valve 100 includes a ferromagneticfree layer 105 including a ferromagnetic layer 106 contacting ananolayer 108 having a first surface 109, a ferromagnetic pinned layer112, and a spacer layer 110, which has a second surface 111, disposedbetween the ferromagnetic free layer 105 and the ferromagnetic pinnedlayer 112. The spin valve 100 may further include an anti-ferromagnetic(AF) layer 114, disposed between the ferromagnetic pinned layer 112 anda cap layer 116, and a oxide seed layer 104 proximate the ferromagneticfree layer 105. The nanolayer 108 enhances the magnetoresistive ratio(ΔR/R) for the spin valve 100.

Ferromagnetic layer 106 typically includes a material containing Ni, Fe,Co or alloys of Ni, Fe and Co such as NiFe, NiCo, and FeCo. Theferromagnetic pinned layer 112 is typically made of Co or CoFe. Thespacer layer 110 is typically made of Cu, Ag, Au or their alloys. The AFlayer 114 typically includes a material containing Mn, such as FeMn,PtMn, IrMn, PdPtMn and NiMn. The nanolayer 108 is typically made ofCoFe, and the cap layer 116 typically includes Ta. Oxide seed layer 104is typically made of NiMnO.

The first surface 109 and the second surface 111 are treated with oxygenduring an ion beam sputtering process of making the spin valve 100. Theoxygen treatment of the surface 109 or 111 occurs after the depositionof the corresponding layer 108 or 110. The first surface 109 may beexposed to oxygen after nanolayer 108 has been deposited. Similarily thesecond surface 111 may be exposed to oxygen after the spacer layer 110has been deposited. Oxygen exposure may be restricted during thedeposition of nanolayer 108 and spacer layer 110. Oxygen treatedsurfaces 109 and 111 limit the intermixing between the nanolayer 108 andthe spacer layer 110, and between the spacer layer 110 and the pinnedlayer 112 respectively. By treating the surface with oxygen afterdeposition of the corresponding layers, higher oxygen partial pressuresmay be used compared to the oxygen partial pressures previously usedwhen treating layers with oxygen during deposition. Consequently, spinvalves such as spin valve 100 may be fabricated with existingmanufacturing type deposition equipment. Furthermore, if oxygen exposureis restricted after deposition, oxygen sensitive layers, such as Mncontaining layers, will not be undesirably exposed to the risk ofoxidation.

These oxygen treated surfaces 109 and 111 reduce the surface roughness,therefore the ferromagnetic coupling H_(f) of the spin valve 100 isreduced. The obtained coupling field H_(f) of spin valve 100 is betweenabout −10 Oe and about +10 Oe, which is stable upon the hard bakeannealing cycles at 232° C. for 11 hours, or at 270° C. for 6 hours. Inaddition, the magnetoresistive ratio ΔR/R of spin valve 100 is alsoenhanced from about 6% to about 9%.

FIG. 2 is a cross sectional schematic diagram illustrating a layerstructure of a bottom AP-pinned spin valve 200 according to a secondembodiment of the present invention. The AP-pinned spin valve 200includes a ferromagnetic free layer 205 including a ferromagnetic layer206 contacting a nanolayer 208, an AP ferromagnetic pinned layer 212,and a spacer layer 210 located between the ferromagnetic free layer 205and the AP-pinned layer 212. The AP-pinned spin valve 200 furtherincludes an AF layer 214 disposed between the AP-pinned layer 212 and ametal seed layer 216, two oxide seed layer 202 and 204 under the metalseed layer 216, and a cap layer 218 disposed on top of the ferromagneticfree layer 206. The material of each layer of AP-pinned spin valve 200,except the AP-pinned layer 212 and the oxide seed layer 202, is similarto those of the corresponding layers of the simple spin valve 100 asdescribed in FIG. 1. The oxide seed layer 202 is typically made ofAl₂O₃.

The AP-pinned layer 212 includes a first ferromagnetic pinned sublayer220, a second ferromagnetic pinned sublayer 224, and an anti-parallel(AP) pinned spacer sublayer 222 between the first pinned sublayer 220and the second pinned sublayer 224. Two ferromagnetic pinned sublayers220 and 224 are typically made of CoFe, the AP pinned spacer sublayer222 is typically made of Ru, Cr, Rh or Cu, or their alloys.

The second ferromagnetic pinned sublayer 224 includes a first surface211, and the spacer layer 210 has a second surface 209. In thisembodiment the first surface 211 corresponds to ferromagnetic pinnedsublayer 224 and the second surface 209 corresponds to the spacer layer210. The first and the second surfaces 211 and 209 are treated withoxygen after depositing corresponding layers 224 and 210. The oxygentreatment generally takes place during the fabrication of the AP-pinnedspin valve 200. The effect of oxygen treated surfaces 209 and 211 on theroughness and the coupling field H_(f) of AP-pinned spin valve 200 issimilar to the effect of oxygen treated surfaces 109 and 111 of simplespin valve 100 as described in FIG. 1. The coupling field H_(f) ofAP-pinned spin valve 200 is around −10 Oe, and the magnetoresistiveratio ΔR/R of AP-pinned spin valve 200 is enhanced from about 5.5% and7.7%.

An ion beam sputtering method may be used to produce spin valves of thetypes depicted in FIGS. 1 and 2 to easily control the deposition betweenwafers or within a wafer. An exemplary sputtering method is disclosed inU.S. Pat. No. 5,871,622 issued Feb. 16, 1999 and U.S. Pat. No. 5,492,605issued Feb. 20, 1996 by the inventor. FIGS. 3A–D are cross-sectionalschematic diagrams illustrating the steps of making spin valves of thetypes depicted in FIGS. 1 and 2. As shown in FIG. 3A, a firstferromagnetic layer 304 is deposited on a substrate 302 in a vacuumchamber. First ferromagnetic layer 304 may be a free layer for a topspin valve or a pinned layer for a bottom spin valve. A first oxygenburst is introduced in to the vacuum chamber with oxygen partialpressure of about 5×10⁻⁶ Torr. A first surface 305 of the firstferromagnetic layer 304 is exposed to this oxygen-rich atmosphere.Oxygen molecules are directed toward the substrate 302 and the substrateshutter, which is not shown in FIG. 3A, is fully open to directly exposefirst surface 305 to the oxygen. As a result, oxygen is physisorbed onthe first surface 305 to produce a first oxygen treated surface 306.

An oxygen valve controlling the flow of oxygen to the chamber is thenshut to reduce the oxygen partial pressure. After the oxygen valve isshut, the deposition process resumes. A spacer layer 308 is deposited onthe first oxygen treated surface 306 which is shown in FIG. 3B. Thespacer layer 308 is deposited over the oxygen treated surface 306 forapproximately 30 seconds and has a thickness of about 20 Å. The spacerlayer 308 has a second surface 309 that is treated with oxygen using amethod similar to the method of treating the first surface 305 withoxygen as described in FIG. 3A. As shown in FIG. 3C, the second surface309 is exposed in an oxygen partial pressure of about 5×10⁻⁶ Torr, andoxygen is physisorbed on the second surface 309 to produce a secondoxygen treated surface 310. Note that the oxygen treatment of surfaces305 and 309 take place after the deposition of the corresponding layers304 and 308. After the oxygen valve is shut off again a secondferromagnetic layer 312, e.g., a ferromagnetic pinned layer for a topspin valve or a ferromagnetic free layer for a bottom spin valve, issubsequently deposited onto the second oxygen treated surface 310 asshown in FIG. 3D.

The process of making the spin valve 300 as described in FIGS. 3A–D doesnot require any additional steps to incorporate the oxygen burst intothe standard spin valve of the prior art. This process may be used fortop and bottom simple spin valves, top and bottom AP-pinned spin valves,and dual spin valves.

EXPERIMENTAL RESULTS

An example is given below to show the oxygen exposure of differentsurfaces and how it affects the coupling field H_(f) of simple top spinvalves. A simple spin valve generally includes an oxide seed layer ofNiMnO 30 Å thick, a free layer including a ferromagnetic layer of NiFe45 Å thick and a nanolayer of CoFe 15 Å thick, a spacer layer of Cu 20 Åthick, a pinned layer of CoFe 24 Å thick, an AF layer of IrMn 80 Åthick, and a cap layer of Ta 50 Å thick. Table 1 below shows theproperties of two simple spin valves A and B, which have the samestructure as described, except for the oxygen exposed surfaces. In spinvalve A only the surface of Cu spacer layer, corresponding to layer 111of FIG. 1, has been exposed to oxygen as described above. In spin valveB, the surfaces of the CoFe layer and Cu spacer layer, corresponding tosurfaces 109 and 111 in FIG. 1, have been treated with oxygen.

TABLE 1 Spin valve A Spin valve B ΔR/R (%) 8.32 8.35 R (Ohms/sq) 20 20H_(f) (Oe) 16 6.5 H_(c) (Oe) 4 5

The data in the Table 1 shows that the coupling field H_(f) is about 2.5times smaller when the spin valve has oxygen exposure of both Cu andCoFe surfaces compared to when the spin valve has oxygen exposure of theCu surface only. The coupling field H_(f) of simple spin valve B doesnot degrade upon hard bake annealing at 232° C. Indeed the spin valve B,which was annealed at 232° C. for 11 hours or at 270° C. for 6 hours,maintained a coupling field at around 8 Oe.

The effect of oxygen surface treatment as described in FIGS. 2–3 on theproperties of bottom AP-pinned PtMn spin valves is shown in FIGS. 4–9. Abottom AP pinned PtMn spin valve generally includes a first oxide seedlayer of Al₂O₃ 30 Å thick, a second oxide seed layer of NiMnO 30 Åthick, a metal seed layer of Ta 35 Å thick, an AF layer of PtMn 250 Åthick, a first pinned sublayer of CoFe 17 Å thick, an AP pinned spacersublayer of Ru 8 Å thick, a second pinned sublayer of CoFe 26 Å thick, aspacer layer of Cu 20 Å thick, a free layer including a ferromagneticlayer of NiFe 45 Å thick and a nanolayer of CoFe 15 Å thick, and a caplayer of Ta 50 Å thick. FIGS. 4–8 are plots of the surface roughness Ra,coupling field H_(f), sheet resistance R, magnetoresistive ratio ΔR/R,and coercive field H_(c) as functions of oxygen flow for an AP-pinnedspin valve of the type depicted in FIG. 2. The spin valve in FIGS. 4–8has a spacer layer about 20 Å thick. As shown in FIG. 4, the surfaceroughness Ra is typically about 2.9 Å when the first and second surfacesare not treated with oxygen. The surface roughness Ra decreases fromabout 2.9 Å to a minimum value of about 1.75 Å as the oxygen flowincreases from zero to about 2 sccm. After this point, the surfaceroughness Ra increases as the oxygen flow increases. Therefore, thesurface roughness is minimized at an oxygen flow of about 2 sccm.(e.g.5×10⁻⁶ Torr oxygen partial pressure)

As shown in FIG. 5, the sheet resistance of an AP-pinned spin valvewithout oxygen surface treatment is typically about 19 Ohms/sq, whichdoes not vary much as the oxygen flow increases. The sheet resistancetypically stays constant when the oxygen flow is in a range of fromabout 1.5 sccm to about 3 sccm. The sheet resistance R is typicallyabout 19 Ohms/sq for an oxygen flow of about 2 sccm.

The improvements of the magnetoresistive ratio ΔR/R and the couplingfield H_(f) of an AP-pinned spin valve are shown in FIGS. 6 and 7respectively. The magnetoresistive ratio ΔR/R is typically about 6% witha coupling field H_(f) of about 56 Oe when the first and second surfacesof the AP spin valve are not treated with oxygen. ΔR/R increases toabout 7.6%, and the coupling field H_(f) decreases rapidly to about 17Oe as the oxygen flow is typically about 0.5 sccm. The coupling fielddecreases from about 17 Oe to about −11 Oe, while ΔR/R of about 7.6%does not vary as the oxygen flow increases from about 0.5 sccm to about2.5 sccm. After this point, ΔR/R typically decreases and the couplingfield H_(f) typically increases as the oxygen flow increases. Thecoupling field H_(f) is about −9 Oe for an oxygen flow of about 2 sccm.

In FIG. 8, the coercive field H_(c) decreases from about 6 Oe to about 5Oe as the oxygen flow increases from zero to about 0.5 sccm. After that,the coercive field slowly increases as the oxygen flow increases. Themaximum value of H_(c) is typically about 7 Oe obtained as an oxygenflow of about 3.5 sccm. The coercive field H_(c) rapidly drops down toabout 2 Oe when the oxygen flow is greater than 3.5 sccm.

FIG. 9 is a graph illustrating the plots of magnetoresistive ratio ΔR/R,sheet resistance R, coupling field H_(f), and coercive field H_(c) asfunctions of spacer layer deposition time with an oxygen flow of about 2sccm. In this case, the spacer layer is made of copper. As shown in FIG.9, the coupling field H_(f) rapidly decreases from about 39 Oe to about−5 Oe as the copper deposition time increases from about 25 seconds toabout 30 seconds. The copper deposition rate is typically about 0.65 Åsecond. After about 30 seconds the coupling field H_(f) typicallyincreases as the copper deposition time increases. The minimum value ofH_(f), which is typically about −5 Oe is obtained after copper isdeposited for about 30 seconds. The sheet resistance R of about 19Ohms/sq, the magnetoresistive ratio ΔR/R of about 7.6%, and the coercivefield H_(c) of 6 Oe are obtained when the deposition of the copperspacer layer is between about 25 seconds to 34 seconds. FIG. 10 is agraph illustrating the plots of coupling field H_(f) andmagnetoresistive ratio ΔR/R, which are depicted in FIG. 9, for the sakeof clarity.

Spin valves of the types described above with respect to FIGS. 1, 2 and3D may be incorporated into a GMR read/write head 404 as shown in FIG.11. The GMR read/write head 404 includes a first shield 403 and secondshield 409 sandwiching a spin valve 401. The GMR read/write head 404further includes a first gap 405 between the first shield 403 and thespin valve 401, and a second gap 407 between the second shield 409 andthe spin valve 401. Spin valve 401 converts a magnetic signal to anelectrical signal by using the magnetoresistive effect generated by arelative angle between magnetization directions of at least twoferromagnetic layers of spin valve 401.

The GMR read/write head depicted in FIG. 11 may be incorporated into adisk drive system 400 as shown in FIG. 12. The disk drive system 400generally comprises a magnetic recording disk 402, a GMR read/write head404 containing a spin valve 401, an actuator 406 connected to theread/write head 404, and a motor 408 connected to the disk 402. Themotor 408 spins the disk 402 with respect to read/write head 404. Theactuator 406 moves the read/write head 404 across the magnetic recordingdisk 402 so the read/write head 404 may access different regions ofmagnetically recorded data on the magnetic recording disk 402.

It will be clear to one skilled in the art that the above embodiment maybe altered in many ways without departing from the scope of theinvention. Accordingly, the scope of the invention should be determinedby the following claims and their legal equivalents.

1. A method for making a spin valve comprising: providing a substrate;depositing a first ferromagnetic layer having a first surface on thesubstrate; depositing a spacer layer having a second surface; depositinga second ferromagnetic layer, wherein the spacer layer is disposedbetween the first and second ferromagnetic layers; and exposing at leastthe first surface to an oxygen partial pressure for causing oxygen tobecome physisorbed onto at least the first surface for forming an oxygentreated surface having a reduced surface roughness, then decreasing theoxygen partial pressure before depositing a subsequent layer onto theoxygen treated surface having reduced surface roughness.
 2. The methodof claim 1, wherein an ion beam sputtering process is used fordepositions of the first ferromagnetic, second ferromagnetic and spacerlayers.
 3. The method of claim 1, wherein oxygen molecules are directedtoward the substrate, and a substrate shutter is fully open for thefirst and second surfaces to be directly exposed to the oxygen, whereinno additional metal is deposited until the oxygen partial pressure isdecreased.
 4. The method of claim 1, wherein the oxygen partial pressureis decreased by stopping a flow of oxygen.
 5. The method of claim 1,wherein the oxygen partial pressure decreases below an oxygen partialpressure level used in exposing the first and second surfaces before thedepositions of the spacer layer and the second ferromagnetic layer. 6.The method of claim 1, wherein the subsequent is deposited prior tosignificant oxidation of the first ferromagnetic layer.
 7. A method formaking a spin valve comprising: providing a substrate; depositing afirst ferromagnetic layer having a first surface on the substrate;depositing a spacer layer having a second surface; depositing a secondferromagnetic layer, wherein the spacer layer is disposed between thefirst and second ferromagnetic layers; and exposing one or more of thefirst and second, surfaces to an oxygen partial pressure for causingoxygen to become physisorbed onto at least one of the first and secondsurfaces for forming at least one of a first oxygen treated surfacehaving a reduced surface roughness and a second oxygen treated surfacehaving a reduced surface roughness, then decreasing the oxygen partialpressure before depositing a subsequent layer onto the at least one ofthe first and second oxygen treated having reduced surface roughness,wherein one or more of the first and second surfaces are exposed to anoxygen partial pressure of between about 1×10⁻⁷ Torr and about 5×10⁻⁵Torr.
 8. The method of claim 7, wherein the oxygen partial pressuredecreases below an oxygen partial pressure level used in exposing thefirst and second surfaces before the depositions of the spacer layer andthe second ferromagnetic layer.
 9. The method of claim 8, wherein thefirst surface is exposed to the oxygen partial pressure beforedepositing the spacer layer.
 10. The method of claim 8, wherein thesecond surface is exposed to the oxygen partial pressure beforedepositing the second ferromagnetic layer.
 11. The method of claim 7,wherein an ion beam sputtering process is used for depositions of thefirst ferromagnetic, second ferromagnetic and spacer layers.
 12. Themethod of claim 7, wherein oxygen molecules are directed toward thesubstrate, and a substrate shutter is fully open for the first andsecond surfaces to be directly exposed to the oxygen, wherein noadditional metal is deposited until the oxygen partial pressure isdecreased.
 13. The method of claim 8, wherein the subsequent layer isdeposited prior to significant oxidation of the first ferromagneticlayer.
 14. A method for making a spin valve comprising: providing asubstrate; depositing, a first ferromagnetic layer having a firstsurface on the substrate; exposing the first surface to an oxygenpartial pressure for causing oxygen to become physisorbed onto the firstsurface for forming a first oxygen treated surface having a reducedsurface roughness relative to the first surface prior to exposure to theoxygen, then decreasing the oxygen partial pressure before depositing asubsequent layer onto the first oxygen treated surface having reducedsurface roughness; depositing a spacer layer above the first surface,the spacer layer having a second surface; exposing the second surface toan oxygen partial pressure for causing oxygen to become physisorbed ontothe second surface for forming a second oxygen treated surface having areduced surface roughness relative to the second surface prior toexposure to the oxygen, then decreasing the oxygen partial pressurebefore depositing a subsequent layer onto the second oxygen treatedsurface having reduced surface roughness; and depositing a secondferromagnetic layer above the second surface, wherein the spacer layeris disposed between the first and second ferromagnetic layers.
 15. Themethod of claim 14, wherein the spacer layer is deposited prior tosignificant oxidation of the first ferromagnetic layer, wherein thesecond ferromagnetic layer is deposited prior to significant oxidationof the spacer layer.